Fish Aggression

[pisces11]

I have six fish im my brand new aquarium. The tank is 21 gallons, with plenty of plastic plants ( i plan to switch with live ones later). I have 3 (young)black lyretail mollies and 3 (young) red platies. The platies (two male, one female) seem to get along fine, with each other and with the mollies. However, although my research and the aquarium store assistant assured me that these fish were ideal for a community tank, the mollies are constantly fighting. Is this just territorial? I can't tell the sex of the fish so I don't know if two males are fighting over a female but it is unlikely, should I leave it alone or is there something I can do??

[daveedka]

If they are damaging or stressing each other (missing scales, torn fins etc.), move them or replace them. if they are just being grumpy without hurting one another I'd give it some time. If you happen to have two males and one female, the female will lose out as the males will both spend all of their time trying to court her, and she'll never get to rest. My fish fight and bicker constantly but seldom do they hurt each other so I don't worry about it other than to pay attention and watch for missing scales.

[dwayne]

I agree with what daveedka said... but you should try to figure out the sex of the mollies.

http://im1.shutterfly.com/procserv/47b4d825b3127ccebff0e6780e2c0000001610

The top red line is pointing to a female's underside fin, and the bottom red line is pointing to a male's gonopodium (sp?, basically it's reproductive organ). I'm 99% sure that all livebearers have this distinction.

Again, as daveedka said, if there are no missing scales or any bite marks, I wouldn't worry about the fighting. But if I were you (imho!) I would change the ratio of your fish to 1 male to 2 females. Livebearers are very "randy" and the males will chase/harrass females, sometimes to the point to stress for the females. So it's always better to have 2 females : 1 male (at the very least, try to have an even # males/females). At least that's been my experience.

Good luck!

~Tara